Light-weight hybrid glass laminates

ABSTRACT

A glass laminate comprises an external glass sheet, an internal glass sheet, and a polymer interlayer formed between the external glass sheet and the internal glass sheet. The external glass sheet can be a thin chemically-strengthened glass sheet or can be a non-chemically strengthened glass sheet, the polymer interlayer can have a thickness of less than 1.6 mm, and the internal glass sheet can be a non-chemically-strengthened glass sheet or a thin chemically strengthened glass sheet.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation of and claims the benefit ofpriority under 35 U.S.C. § 120 of U.S. patent application Ser. No.17/401,980, filed on Aug. 13, 2021, which is a continuation and claimsthe benefit of priority under 35 U.S.C. § 120 of U.S. patent applicationSer. No. 16/002,194, filed on Jun. 7, 2018, which is a continuation andclaims the benefit of priority under 35 U.S.C. § 120 of U.S. patentapplication Ser. No. 15/207,993, filed Jul. 12, 2016, now patent Ser.No. 10/035,332, granted Jul. 31, 2018, which is a continuation andclaims the benefit of priority under 35 U.S.C. § 120 of U.S. patentapplication Ser. No. 13/937,707 filed Jul. 9, 2013, now U.S. Pat. No.9,616,641, granted Apr. 11, 2017, which is a continuation-in-partapplication of and claims the benefit of priority under 35 U.S.C. § 120of U.S. patent application Ser. No. 13/247,182, filed on Sep. 28, 2011,now patent Ser. No. 10/035,331, granted Jul. 31, 2018, which in turn,claims the benefit of priority under 35 U.S.C. § 119 of U.S. ProvisionalApplication Ser. No. 61/500,766 filed on Jun. 24, 2011, the content ofeach being relied upon and incorporated herein by reference in theirentirety.

BACKGROUND

The present disclosure relates generally to glass laminates, and moreparticularly to hybrid glass laminates comprising achemically-strengthened outer glass pane and anon-chemically-strengthened inner glass pane. Such hybrid laminates maybe characterized by low weight, good sound-damping performance, and highimpact resistance. In particular, the disclosed hybrid laminates satisfycommercially-applicable impact test criteria for non-windscreenapplications.

Glass laminates can be used as windows and glazings in architectural andtransportation applications, including automobiles, rolling stock andairplanes. As used herein, a glazing is a transparent orsemi-transparent part of a wall or other structure. Common types ofglazings that are used in architectural and automotive applicationsinclude clear and tinted glass, including laminated glass. Laminatedglazings comprising opposing glass sheets separated by a plasticizedpoly(vinyl butyral) (PVB) sheet, for example, can be used as windows,windshields, or sunroofs. In certain applications, glass laminateshaving high mechanical strength and sound-attenuating properties aredesirable in order to provide a safe barrier while reducing soundtransmission from external sources.

In many vehicular applications, fuel economy is a function of vehicleweight. It is desirable, therefore, to reduce the weight of glazings forsuch applications without compromising strength and sound-attenuatingproperties. In this regard, it can be advantageous for a glass laminateto be mechanically robust with respect to external impact events such asattempted forced entry or contact with stones or hail, yet suitablydissipate energy (and fracture) as a result of internal impact eventssuch as contact with an occupant, for example, during a collision.Further, governmental regulations are demanding higher fuel mileage andlower carbon dioxide emissions for road vehicles. Thus, there has beenan increased effort to reduce the weight of these vehicles whilemaintaining current governmental and industry safety standards.Non-glass window materials, such as polycarbonate, have been developed,which reduce vehicle weight but do not offer appropriate resistance toenvironmental, debris, and other concerns. Embodiments of the presentdisclosure, however, provide substantial weight reduction, safetycompliance, effective durability and reduced laceration potential in theevent of a vehicular crash. In view of the foregoing, thin, light weightglazings that possess the durability and sound-damping propertiesassociated with thicker, heavier glazings are desirable.

SUMMARY

According to one aspect of the disclosure, a glass laminate comprises anexternal glass sheet, an internal glass sheet, and a polymer interlayerformed between the external and internal glass sheets. In order tooptimize the impact behavior of the glass laminate, the external glasssheet comprises chemically-strengthened glass and can have a thicknessof less than or equal to 1 mm, while the internal glass sheet comprisesnon-chemically-strengthened glass and can have a thickness of less thanor equal to 2.5 mm. In embodiments, the polymer interlayer (e.g.,poly(vinyl butyral) or PVB) can have a thickness of less than or equalto 1.6 mm. The disclosed hybrid glass laminate architecture canadvantageously distribute stresses in response to impact. For example,the disclosed glass laminates can provide superior impact resistance andresist breakage in response to external impact events, yet appropriatelydissipate energy and appropriately fracture in response to internalimpact events.

One non-limiting embodiment of the present disclosure provides a glasslaminate structure having a non-chemically strengthened external glasssheet, a chemically strengthened internal glass sheet, and at least onepolymer interlayer intermediate the external and internal glass sheets,where the internal glass sheet has a thickness ranging from about 0.5 mmto about 1.5 mm and where the external glass sheet has a thicknessranging from about 1.5 mm to about 3.0 mm.

Another non-limiting embodiment of the present disclosure provides aglass laminate structure having a non-chemically strengthened externalglass sheet, a chemically strengthened internal glass sheet, and atleast one polymer interlayer intermediate the external and internalglass sheets, where the inner glass layer has a surface compressivestress between about 250 MPa and about 900 MPa.

Additional features and advantages of the claimed subject matter will beset forth in the detailed description which follows, and in part will bereadily apparent to those skilled in the art from that description orrecognized by practicing the claimed subject matter as described herein,including the detailed description which follows, the claims, as well asthe appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description present embodiments of the presentdisclosure, and are intended to provide an overview or framework forunderstanding the nature and character of the claimed subject matter.The accompanying drawings are included to provide a furtherunderstanding of the present disclosure, and are incorporated into andconstitute a part of this specification. The drawings illustrate variousembodiments and together with the description serve to explain theprinciples and operations of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purposes of illustration, there are forms shown in the drawingsthat are presently preferred, it being understood, however, that theembodiments disclosed and discussed herein are not limited to theprecise arrangements and instrumentalities shown.

FIG. 1 is a schematic of an exemplary planar hybrid glass laminateaccording to some embodiments of the present disclosure.

FIG. 2 is a schematic of an exemplary bent hybrid glass laminateaccording to other embodiments of the present disclosure.

FIG. 3 is a schematic of an exemplary bent hybrid glass laminateaccording to further embodiments of the present disclosure.

FIG. 4 is a schematic of an exemplary bent hybrid glass laminateaccording to additional embodiments of the present disclosure.

DETAILED DESCRIPTION

In the following description, like reference characters designate likeor corresponding parts throughout the several views shown in thefigures. It is also understood that, unless otherwise specified, termssuch as “top,” “bottom,” “outward,” “inward,” and the like are words ofconvenience and are not to be construed as limiting terms. In addition,whenever a group is described as comprising at least one of a group ofelements and combinations thereof, it is understood that the group maycomprise, consist essentially of, or consist of any number of thoseelements recited, either individually or in combination with each other.

Similarly, whenever a group is described as consisting of at least oneof a group of elements or combinations thereof, it is understood thatthe group may consist of any number of those elements recited, eitherindividually or in combination with each other. Unless otherwisespecified, a range of values, when recited, includes both the upper andlower limits of the range. As used herein, the indefinite articles “a,”and “an,” and the corresponding definite article “the” mean “at leastone” or “one or more,” unless otherwise specified.

The following description of the present disclosure is provided as anenabling teaching thereof and its best, currently-known embodiment.Those skilled in the art will recognize that many changes can be made tothe embodiment described herein while still obtaining the beneficialresults of the present disclosure. It will also be apparent that some ofthe desired benefits of the present disclosure can be obtained byselecting some of the features of the present disclosure withoututilizing other features. Accordingly, those who work in the art willrecognize that many modifications and adaptations of the presentdisclosure are possible and may even be desirable in certaincircumstances and are part of the present disclosure. Thus, thefollowing description is provided as illustrative of the principles ofthe present disclosure and not in limitation thereof.

Those skilled in the art will appreciate that many modifications to theexemplary embodiments described herein are possible without departingfrom the spirit and scope of the present disclosure. Thus, thedescription is not intended and should not be construed to be limited tothe examples given but should be granted the full breadth of protectionafforded by the appended claims and equivalents thereto. In addition, itis possible to use some of the features of the present disclosurewithout the corresponding use of other features. Accordingly, thefollowing description of exemplary or illustrative embodiments isprovided for the purpose of illustrating the principles of the presentdisclosure and not in limitation thereof and may include modificationthereto and permutations thereof.

The glass laminates disclosed herein are configured to include anexternal chemically-strengthened glass sheet and an internalnon-chemically-strengthened glass sheet. As defined herein, when theglass laminates are put into use, an external glass sheet will beproximate to or in contact the environment, while an internal glasssheet will be proximate to or in contact with the interior (e.g., cabin)of the structure or vehicle (e.g., automobile) incorporating the glasslaminate.

An exemplary glass laminate is illustrated in FIG. 1 . The glasslaminate 100 comprises an external glass sheet 110, an internal glasssheet 120, and a polymer interlayer 130. The polymer interlayer can bein direct physical contact (e.g., laminated to) each of the respectiveexternal and internal glass sheets. The external glass sheet 110 has anexterior surface 112 and an interior surface 114. In a similar vein, theinternal glass sheet 120 has an exterior surface 122 and an interiorsurface 124. As shown in the illustrated embodiment, the interiorsurface 114 of external glass sheet 110 and the interior surface 124 ofinternal glass sheet 120 are each in contact with polymer interlayer130.

During use, it is desirable that the glass laminates resist fracture inresponse to external impact events. In response to internal impactevents, however, such as the glass laminates being struck by a vehicle'soccupant, it is desirable that the glass laminate retain the occupant inthe vehicle yet dissipate energy upon impact in order to minimizeinjury. The ECE R43 headform test, which simulates impact eventsoccurring from inside a vehicle, is a regulatory test that requires thatlaminated glazings fracture in response to specified internal impact.

Without wishing to be bound by theory, when one pane of a glasssheet/polymer interlayer/glass sheet laminate is impacted, the oppositesurface of the impacted sheet, as well as the exterior surface of theopposing sheet are placed into tension. Calculated stress distributionsfor a glass sheet/polymer interlayer/glass sheet laminate under biaxialloading reveal that the magnitude of tensile stress in the oppositesurface of the impacted sheet may be comparable to (or even slightlygreater than) the magnitude of the tensile stress experienced at theexterior surface of the opposing sheet for low loading rates. However,for high loading rates, which are characteristic of impacts typicallyexperienced in automobiles, the magnitude of the tensile stress at theexterior surface of the opposing sheet may be much greater than thetensile stress at the opposite surface of the impacted sheet. Asdisclosed herein, by configuring the hybrid glass laminates to have achemically-strengthened external glass sheet and anon-chemically-strengthened internal glass sheet, the impact resistancefor both external and internal impact events can be optimized.

Suitable internal glass sheets are non-chemically-strengthened glasssheets such as soda-lime glass. Optionally, the internal glass sheetsmay be heat strengthened. In embodiments where soda-lime glass is usedas the non-chemically-strengthened glass sheet, conventional decoratingmaterials and methods (e.g., glass frit enamels and screen printing) canbe used, which can simplify the glass laminate manufacturing process.Tinted soda-lime glass sheets can be incorporated into a hybrid glasslaminate in order to achieve desired transmission and/or attenuationacross the electromagnetic spectrum.

Suitable external glass sheets may be chemically strengthened by an ionexchange process. In this process, typically by immersion of the glasssheet into a molten salt bath for a predetermined period of time, ionsat or near the surface of the glass sheet are exchanged for larger metalions from the salt bath. In one embodiment, the temperature of themolten salt bath is about 430° C. and the predetermined time period isabout eight hours. The incorporation of the larger ions into the glassstrengthens the sheet by creating a compressive stress in a near surfaceregion. A corresponding tensile stress is induced within a centralregion of the glass to balance the compressive stress.

Exemplary ion-exchangeable glasses that are suitable for forming hybridglass laminates are alkali aluminosilicate glasses or alkalialuminoborosilicate glasses, though other glass compositions arecontemplated. As used herein, “ion exchangeable” means that a glass iscapable of exchanging cations located at or near the surface of theglass with cations of the same valence that are either larger or smallerin size. One exemplary glass composition comprises SiO₂, B₂O₃ and Na₂O,where (SiO₂+B₂O₃)≥66 mol. %, and Na₂O≥9 mol. %. In an embodiment, theglass sheets include at least 6 wt. % aluminum oxide. In a furtherembodiment, a glass sheet includes one or more alkaline earth oxides,such that a content of alkaline earth oxides is at least 5 wt. %.Suitable glass compositions, in some embodiments, further comprise atleast one of K₂O, MgO, and CaO. In a particular embodiment, the glasscan comprise 61-75 mol. % SiO₂; 7-15 mol. % Al₂O₃; 0-12 mol. % B₂O₃;9-21 mol. % Na₂O; 0-4 mol. % K₂O; 0-7 mol. % MgO; and 0-3 mol. % CaO.

A further exemplary glass composition suitable for forming hybrid glasslaminates comprises: 60-70 mol. % SiO₂; 6-14 mol. % Al₂O₃; 0-15 mol. %B₂O₃; 0-15 mol. % Li₂O; 0-20 mol. % Na₂O; 0-10 mol. % K₂O; 0-8 mol. %MgO; 0-10 mol. % CaO; 0-5 mol. % ZrO₂; 0-1 mol. % SnO₂; 0-1 mol. % CeO₂;less than 50 ppm As₂O₃; and less than 50 ppm Sb₂O₃; where 12 mol.%≤(Li₂O+Na₂O+K₂O)≤20 mol. % and 0 mol. %≤(MgO+CaO)≤10 mol. %.

A still further exemplary glass composition comprises: 63.5-66.5 mol. %SiO₂; 8-12 mol. % Al₂O₃; 0-3 mol. % B₂O₃; 0-5 mol. % Li₂O; 8-18 mol. %Na₂O; 0-5 mol. % K₂O; 1-7 mol. % MgO; 0-2.5 mol. % CaO; 0-3 mol. % ZrO₂;0.05-0.25 mol. % SnO₂; 0.05-0.5 mol. % CeO₂; less than 50 ppm As₂O₃; andless than 50 ppm Sb₂O₃; where 14 mol. % (Li₂O+Na₂O+K₂O) 18 mol. % and 2mol. % (MgO+CaO) 7 mol. %.

In a particular embodiment, an alkali aluminosilicate glass comprisesalumina, at least one alkali metal and, in some embodiments, greaterthan 50 mol. % SiO₂, in other embodiments at least 58 mol. % SiO₂, andin still other embodiments at least 60 mol. % SiO₂, wherein the ratio

${\frac{{{Al}_{2}O_{3}} + {B_{2}O_{3}}}{\sum{modifiers}} > 1},$

where in the ratio the components are expressed in mol. % and themodifiers are alkali metal oxides. This glass, in particularembodiments, comprises, consists essentially of, or consists of: 58-72mol. % SiO₂; 9-17 mol. % Al₂O₃; 2-12 mol. % B₂O₃; 8-16 mol. % Na₂O; and0-4 mol. % K₂O, wherein the ratio

$\frac{{{Al}_{2}O_{3}} + {B_{2}O_{3}}}{\sum{modifiers}} > 1.$

In another embodiment, an alkali aluminosilicate glass comprises,consists essentially of, or consists of: 61-75 mol. % SiO₂; 7-15 mol. %Al₂O₃; 0-12 mol. % B₂O₃; 9-21 mol. % Na₂O; 0-4 mol. % K₂O; 0-7 mol. %MgO; and 0-3 mol. % CaO.

In yet another embodiment, an alkali aluminosilicate glass substratecomprises, consists essentially of, or consists of: 60-70 mol. % SiO₂;6-14 mol. % Al₂O₃; 0-15 mol. % B₂O₃; 0-15 mol. % Li₂O; 0-20 mol. % Na₂O;0-10 mol. % K₂O; 0-8 mol. % MgO; 0-10 mol. % CaO; 0-5 mol. % ZrO₂; 0-1mol. % SnO₂; 0-1 mol. % CeO₂; less than 50 ppm As₂O₃; and less than 50ppm Sb₂O₃; wherein 12 mol. %≤Li₂O+Na₂O+K₂O≤20 mol. % and 0 mol.%≤MgO+CaO≤10 mol. %.

In still another embodiment, an alkali aluminosilicate glass comprises,consists essentially of, or consists of: 64-68 mol. % SiO₂; 12-16 mol. %Na₂O; 8-12 mol. % Al₂O₃; 0-3 mol. % B₂O₃; 2-5 mol. % K₂O; 4-6 mol. %MgO; and 0-5 mol. % CaO, wherein: 66 mol. % SiO₂+B₂O₃+CaO≤69 mol. %;Na₂O+K₂O+B₂O₃+MgO+CaO+SrO>10 mol. %; 5 mol. %≤MgO+CaO+SrO≤8 mol. %;(Na₂O+B₂O₃)—Al₂O₃≤2 mol. %; 2 mol. %≤Na₂O—Al₂O₃≤6 mol. %; and 4 mol.%≤(Na₂O+K₂O)—Al₂O₃≤10 mol. %.

The chemically-strengthened as well as the non-chemically-strengthenedglass, in some embodiments, is batched with 0-2 mol. % of at least onefining agent selected from a group that includes Na₂SO₄, NaCl, NaF,NaBr, K₂SO₄, KCl, KF, KBr, and SnO₂.

In one exemplary embodiment, sodium ions in the chemically-strengthenedglass can be replaced by potassium ions from the molten bath, thoughother alkali metal ions having a larger atomic radii, such as rubidiumor cesium, can replace smaller alkali metal ions in the glass. Accordingto particular embodiments, smaller alkali metal ions in the glass can bereplaced by Ag⁺ ions. Similarly, other alkali metal salts such as, butnot limited to, sulfates, halides, and the like may be used in the ionexchange process.

The replacement of smaller ions by larger ions at a temperature belowthat at which the glass network can relax produces a distribution ofions across the surface of the glass that results in a stress profile.The larger volume of the incoming ion produces a compressive stress (CS)on the surface and tension (central tension, or CT) in the center of theglass. The compressive stress is related to the central tension by thefollowing relationship:

${CS} = {C{T\left( \frac{t - {2DOL}}{DOL} \right)}}$

where t is the total thickness of the glass sheet and DOL is the depthof exchange, also referred to as depth of layer.

According to various embodiments, hybrid glass laminates comprisingion-exchanged glass possess an array of desired properties, includinglow weight, high impact resistance, and improved sound attenuation.

In one embodiment, a chemically-strengthened glass sheet can have asurface compressive stress of at least 300 MPa, e.g., at least 400, 450,500, 550, 600, 650, 700, 750 or 800 MPa, a depth of layer at least about20 μm (e.g., at least about 20, 25, 30, 35, 40, 45, or 50 μm) and/or acentral tension greater than 40 MPa (e.g., greater than 40, 45, or 50MPa) but less than 100 MPa (e.g., less than 100, 95, 90, 85, 80, 75, 70,65, 60, or 55 MPa).

A modulus of elasticity of a chemically-strengthened glass sheet canrange from about 60 GPa to 85 GPa (e.g., 60, 65, 70, 75, 80 or 85 GPa).The modulus of elasticity of the glass sheet(s) and the polymerinterlayer can affect both the mechanical properties (e.g., deflectionand strength) and the acoustic performance (e.g., transmission loss) ofthe resulting glass laminate.

Exemplary glass sheet forming methods include fusion draw and slot drawprocesses, which are each examples of a down-draw process, as well asfloat processes. These methods can be used to form bothchemically-strengthened and non-chemically-strengthened glass sheets.The fusion draw process uses a drawing tank that has a channel foraccepting molten glass raw material. The channel has weirs that are openat the top along the length of the channel on both sides of the channel.When the channel fills with molten material, the molten glass overflowsthe weirs. Due to gravity, the molten glass flows down the outsidesurfaces of the drawing tank. These outside surfaces extend down andinwardly so that they join at an edge below the drawing tank. The twoflowing glass surfaces join at this edge to fuse and form a singleflowing sheet. The fusion draw method offers the advantage that, becausethe two glass films flowing over the channel fuse together, neitheroutside surface of the resulting glass sheet comes in contact with anypart of the apparatus. Thus, the surface properties of the fusion drawnglass sheet are not affected by such contact.

The slot draw method is distinct from the fusion draw method. Here themolten raw material glass is provided to a drawing tank. The bottom ofthe drawing tank has an open slot with a nozzle that extends the lengthof the slot. The molten glass flows through the slot/nozzle and is drawndownward as a continuous sheet and into an annealing region. The slotdraw process can provide a thinner sheet than the fusion draw processbecause only a single sheet is drawn through the slot, rather than twosheets being fused together.

Down-draw processes produce glass sheets having a uniform thickness thatpossess surfaces that are relatively pristine. Because the strength ofthe glass surface is controlled by the amount and size of surface flaws,a pristine surface that has had minimal contact has a higher initialstrength. When this high strength glass is then chemically strengthened,the resultant strength can be higher than that of a surface that hasbeen a lapped and polished. Down-drawn glass may be drawn to a thicknessof less than about 2 mm. In addition, down drawn glass has a very flat,smooth surface that can be used in its final application without costlygrinding and polishing.

In the float glass method, a sheet of glass that may be characterized bysmooth surfaces and uniform thickness is made by floating molten glasson a bed of molten metal, typically tin. In an exemplary process, moltenglass that is fed onto the surface of the molten tin bed forms afloating ribbon. As the glass ribbon flows along the tin bath, thetemperature is gradually decreased until a solid glass sheet can belifted from the tin onto rollers. Once off the bath, the glass sheet canbe cooled further and annealed to reduce internal stress.

Glass sheets can be used to form glass laminates. As defined herein, ahybrid glass laminate comprises an externally-facingchemically-strengthened glass sheet, an internally-facingnon-chemically-strengthened glass sheet, and a polymer interlayer formedbetween the glass sheets. The polymer interlayer can comprise amonolithic polymer sheet, a multilayer polymer sheet, or a compositepolymer sheet. The polymer interlayer can be, for example, a plasticizedpoly(vinyl butyral) sheet.

Glass laminates can be adapted to provide an optically transparentbarrier in architectural and automotive openings, e.g., automotiveglazings. Glass laminates can be formed using a variety of processes.The assembly, in an exemplary embodiment, involves laying down a firstsheet of glass, overlaying a polymer interlayer such as a PVB sheet,laying down a second sheet of glass, and then trimming the excess PVB tothe edges of the glass sheets. A tacking step can include expelling mostof the air from the interfaces and partially bonding the PVB to theglass sheets. The finishing step, typically carried out at elevatedtemperature and pressure, completes the mating of each of the glasssheets to the polymer interlayer. In the foregoing embodiment, the firstsheet can be a chemically-strengthened glass sheet and the second sheetcan be a non-chemically-strengthened glass sheet or vice versa.

A thermoplastic material such as PVB may be applied as a preformedpolymer interlayer. The thermoplastic layer can, in certain embodiments,have a thickness of at least 0.125 mm (e.g., 0.125, 0.25, 0.38, 0.5,0.7, 0.76, 0.81, 1, 1.14, 1.19 or 1.2 mm) The thermoplastic layer canhave a thickness of less than or equal to 1.6 mm (e.g., from 0.4 to 1.2mm, such as about 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1 or 1.2 mm) Thethermoplastic layer can cover most or, preferably, substantially all ofthe two opposed major faces of the glass. It may also cover the edgefaces of the glass. The glass sheets in contact with the thermoplasticlayer may be heated above the softening point of the thermoplastic, suchas, for example, at least 5° C. or 10° C. above the softening point, topromote bonding of the thermoplastic material to the respective glasssheets. The heating can be performed with the glass in contact with thethermoplastic layers under pressure.

Select commercially available polymer interlayer materials aresummarized in Table 1, which provides also the glass transitiontemperature and modulus for each product sample. Glass transitiontemperature and modulus data were determined from technical data sheetsavailable from the vendor or using a DSC 200 Differential Scanningcalorimeter (Seiko Instruments Corp., Japan) or by ASTM D638 method forthe glass transition and modulus data, respectively. A furtherdescription of the acrylic/silicone resin materials used in the ISDresin is disclosed in U.S. Pat. No. 5,624,763, and a description of theacoustic modified PVB resin is disclosed in Japanese Patent No.05138840, the entire contents of which are hereby incorporated byreference in their entirety.

TABLE 1 Exemplary Polymer Interlayer Materials T_(g) Modulus, psiInterlayer Material (° C.) (MPa) EVA (STR Corp., Enfield, CT) −20750-900 (5.2-6.2) EMA (Exxon Chemical Co., Baytown, TX) −55 <4,500(27.6) EMAC (Chevron Corp., Orange, TX) −57 <5,000 (34.5) PVCplasticized (Geon Company, Avon −45 <1500 (10.3) Lake, OH) PVBplasticized (Solutia, St. Louis, MO) 0 <5000 (34.5) Polyethylene,Metallocene-catalyzed −60 <11,000 (75.9) (Exxon Chemical Co., Baytown,TX) Polyurethane Hard (97 Shore A) 31 400 Polyurethane Semi-rigid (78Shore A) −49 54 ISD resin (3M Corp., Minneapolis, MN) −20 Acousticmodified PVB (Sekisui KKK, 140 Osaka, Japan) Uvekol A (liquid curableresins) (Cytec, Woodland Park, NJ)

One or more polymer interlayers may be incorporated into a hybrid glasslaminate. A plurality of interlayers may provide complimentary ordistinct functionality, including adhesion promotion, acoustic control,UV transmission control, tinting, coloration and/or IR transmissioncontrol.

A modulus of elasticity of the polymer interlayer can range from about 1MPa to 75 MPa (e.g., about 1, 2, 5, 10, 15, 20, 25, 50 or 75 MPa). At aloading rate of 1 Hz, a modulus of elasticity of a standard PVBinterlayer can be about 15 MPa, and a modulus of elasticity of anacoustic grade PVB interlayer can be about 2 MPa.

During the lamination process, the interlayer is typically heated to atemperature effective to soften the interlayer, which promotes aconformal mating of the interlayer to respective surfaces of the glasssheets. For PVB, a lamination temperature can be about 140° C. Mobilepolymer chains within the interlayer material develop bonds with theglass surfaces, which promote adhesion. Elevated temperatures alsoaccelerate the diffusion of residual air and/or moisture from theglass-polymer interface.

The application of pressure both promotes flow of the interlayermaterial, and suppresses bubble formation that otherwise could beinduced by the combined vapor pressure of water and air trapped at theinterfaces. To suppress bubble formation, heat and pressure aresimultaneously applied to the assembly in an autoclave.

Hybrid glass laminates can provide beneficial effects, including theattenuation of acoustic noise, reduction of UV and/or IR lighttransmission, and/or enhancement of the aesthetic appeal of a windowopening. The individual glass sheets comprising the disclosed glasslaminates, as well as the formed laminates, can be characterized by oneor more attributes, including composition, density, thickness, surfacemetrology, as well as various properties including optical,sound-attenuation, and mechanical properties such as impact resistance.Various aspects of the disclosed hybrid glass laminates are describedherein.

The hybrid glass laminates can be adapted for use, for example, aswindows or glazings, and configured to any suitable size and dimension.In embodiments, the glass laminates have a length and width thatindependently vary from 10 cm to 1 m or more (e.g., 0.1, 0.2, 0.5, 1, 2,or 5 m). Independently, the glass laminates can have an area of greaterthan 0.1 m², e.g., greater than 0.1, 0.2, 0.5, 1, 2, 5, 10, or 25 m².

The glass laminates can be substantially flat or shaped for certainapplications. For instance, the glass laminates can be formed as bent orshaped parts for use as windshields or cover plates. The structure of ashaped glass laminate may be simple or complex. In certain embodiments,a shaped glass laminate may have a complex curvature where the glasssheets have a distinct radius of curvature in two independentdirections. Such shaped glass sheets may thus be characterized as having“cross curvature,” where the glass is curved along an axis that isparallel to a given dimension and also curved along an axis that isperpendicular to the same dimension. An automobile sunroof, for example,typically measures about 0.5 m by 1.0 m and has a radius of curvature of2 to 2.5 m along the minor axis, and a radius of curvature of 4 to 5 malong the major axis.

Shaped glass laminates according to certain embodiments can be definedby a bend factor, where the bend factor for a given part is equal to theradius of curvature along a given axis divided by the length of thataxis. Thus, for the exemplary automotive sunroof having radii ofcurvature of 2 m and 4 m along respective axes of 0.5 m and 1.0 m, thebend factor along each axis is 4. Shaped glass laminates can have a bendfactor ranging from 2 to 8 (e.g., 2, 3, 4, 5, 6, 7, or 8).

An exemplary shaped glass laminate 200 is illustrated in FIG. 2 . Theshaped laminate 200 comprises an external (chemically-strengthened)glass sheet 110 formed at a convex surface of the laminate while aninternal (non-chemically-strengthened) glass sheet 120 is formed on aconcave surface of the laminate. It will be appreciated, however, thatthe convex surface of a non-illustrated embodiment can comprise anon-chemically-strengthened glass sheet while an opposing concavesurface can comprise a chemically-strengthened glass sheet.

FIG. 3 is a cross sectional illustration of further embodiments of thepresent disclosure. FIG. 4 is a perspective view of additionalembodiments of the present disclosure. With reference to FIGS. 3 and 4and as discussed in previous paragraphs, an exemplary laminate structure10 can include an inner layer 16 of chemically strengthened glass, e.g.,Gorilla® Glass. This inner layer 16 may have been heat treated, ionexchanged and/or annealed. The outer layer 12 may be a non-chemicallystrengthened glass sheet such as conventional soda lime glass, annealedglass, or the like. The laminate 10 can also include a polymericinterlayer 14 intermediate the outer and inner glass layers. The innerlayer of glass 16 can have a thickness of less than or equal to 1.0 mmand having a residual surface CS level of between about 250 MPa to about350 MPa with a DOL of greater than 60 microns. In another embodiment theCS level of the inner layer 16 is preferably about 300 MPa. In oneembodiment, an interlayer 14 can have a thickness of approximately 0.8mm Exemplary interlayers 14 can include, but are not limited to,poly-vinyl-butyral or other suitable polymeric materials as describedherein. In additional embodiments, any of the surfaces of the outerand/or inner layers 12, 16 can be acid etched to improve durability toexternal impact events. For example, in one embodiment, a first surface13 of the outer layer 12 can be acid etched and/or another surface 17 ofthe inner layer can be acid etched. In another embodiment, a firstsurface 15 of the outer layer can be acid etched and/or another surface19 of the inner layer can be acid etched. Such embodiments can thusprovide a laminate construction substantially lighter than conventionallaminate structures and which conforms to regulatory impactrequirements. Exemplary thicknesses of the outer and/or inner layers 12,16 can range in thicknesses from 0.5 mm to 1.5 mm to 2.0 mm or more.

In a preferred embodiment, the thin chemically strengthened inner layer16 may have a surface stress between about 250 MPa and 900 MPa and canrange in thickness from 0.5 to 1.0 mm. In this embodiment, the externallayer 12 can be annealed (non-chemically strengthened) glass with athickness from about 1.5 mm to about 3.0 mm or more. Of course, thethicknesses of the outer and inner layers 12, 16 can be different in arespective laminate structure 10. Another preferred embodiment of anexemplary laminate structure may include an inner layer of 0.7 mmchemically strengthened glass, a poly-vinyl butyral layer of about 0.76mm in thickness and a 2.1 mm exterior layer of annealed glass.

Exemplary glass layers can be made by fusion drawing, as generallydescribed above and described in U.S. Pat. Nos. 7,666,511, 4,483,700 and5,674,790, the entirety of each being incorporated herein by reference,and then chemically strengthening such drawn glass. Exemplary chemicallystrengthened glass layers can thus possess a deep DOL of CS and canpresent a high flexural strength, scratch resistance and impactresistance. Exemplary embodiments can also include acid etched or flaredsurfaces to increase the impact resistance and increasing the strengthof such surfaces by reducing the size and severity of flaws on thesesurfaces. If etched immediately prior to lamination, the strengtheningbenefit of etching or flaring can be maintained on surfaces bonded tothe inter-layer.

One embodiment of the present disclosure provides an exemplary glasslaminate structure having a non-chemically strengthened external glasssheet, a chemically strengthened internal glass sheet, and at least onepolymer interlayer intermediate the external and internal glass sheets.The polymer interlayer can be a single polymer sheet, a multilayerpolymer sheet, or a composite polymer sheet. Further, the polymerinterlayer can comprise a material such as, but not limited to, PVB,polycarbonate, acoustic PVB, ethylene vinyl acetate (EVA), thermoplasticpolyurethane (TPU), ionomer, a thermoplastic material, and combinationsthereof. The internal glass sheet can have a thickness ranging fromabout 0.5 mm to about 1.5 mm, and the external glass sheet can have athickness ranging from about 1.5 mm to about 3.0 mm. In otherembodiments, the internal glass sheet can have a thickness of betweenabout 0.5 mm to about 0.7 mm, the polymer interlayer can have athickness of between about 0.4 to about 1.2 mm, and/or the externalglass sheet can have a thickness of about 2.1 mm. In another embodiment,the internal glass sheet can include one or more alkaline earth oxides,such that a content of alkaline earth oxides is at least about 5 wt. %.The internal glass sheet can also include at least about 6 wt. %aluminum oxide. In an additional embodiment, the external glass sheetcomprises a material such as, but not limited to, soda-lime glass andannealed glass. Exemplary laminates can have an area greater than 1 m²and can be employed as an automotive windshield, sunroof or cover plate.In further embodiments, the inner glass layer can have a surfacecompressive stress between about 250 MPa and about 900 MPa or in anotherembodiment, a surface compressive stress of between about 250 MPa andabout 350 MPa and a DOL of compressive stress greater than about 20 μm.Some embodiments, can acid etch any number or portion of the surfaces ofthe glass sheets.

Another embodiment of the present disclosure provides a glass laminatestructure having a non-chemically strengthened external glass sheet, achemically strengthened internal glass sheet, and at least one polymerinterlayer intermediate the external and internal glass sheets where theinner glass layer has a surface compressive stress between about 250 MPaand about 900 MPa. In an additional embodiment, the inner glass layercan have a surface compressive stress of between about 250 MPa and about350 MPa and a DOL of compressive stress greater than about 20 μm.Exemplary thicknesses of the internal glass sheet can range from about0.5 mm to about 1.5 mm, and the external glass sheet can havethicknesses ranging from about 1.5 mm to about 3.0 mm. An exemplarypolymer interlayer can be comprised of a material such as, but notlimited to, PVB, polycarbonate, acoustic PVB, EVA, TPU, ionomer, athermoplastic material, and combinations thereof and/or can have athickness of between about 0.4 to about 1.2 mm.

Embodiments of the present disclosure may thus offer a means to reducethe weight of automotive glazing by using thinner glass materials whilemaintaining optical and safety requirements. Conventional laminatedwindshields may account for 62% of a vehicle's total glazing weight;however, by employing a 0.7-mm thick chemically strengthened inner layerwith a 2.1-mm thick non-chemically strengthened outer layer, forexample, windshield weight can be reduced by 33%. Furthermore, it hasbeen discovered that use of a 1.6-mm thick non-chemically strengthenedouter layer with the 0.7-mm thick chemically strengthened inner layerresults in an overall 45% weight savings. Thus, use of exemplarylaminate structures according to embodiments of the present disclosuremay allow a laminated windshield to pass all regulatory safetyrequirements including resistance to penetration from internal andexternal objects and appropriate flexure resulting in acceptable HeadImpact Criteria (HIC) values. In addition, an exemplary external layercomprised of annealed glass may offer acceptable break patterns causedby external object impacts and allow for continued operationalvisibility through the windshield when a chip or crack occurs as aresult of the impact. Research has also demonstrated that employingchemically strengthened glass as an interior surface of an asymmetricalwindshield provides an added benefit of reduced laceration potentialcompared to that caused by occupant impact with conventional annealedwindshields.

Methods for bending and/or shaping glass laminates can include gravitybending, press bending and methods that are hybrids thereof. In atraditional method of gravity bending thin, flat sheets of glass intocurved shapes such as automobile windshields, cold, pre-cut single ormultiple glass sheets are placed onto the rigid, pre-shaped, peripheralsupport surface of a bending fixture. The bending fixture may be madeusing a metal or a refractory material. In an exemplary method, anarticulating bending fixture may be used. Prior to bending, the glasstypically is supported only at a few contact points. The glass isheated, usually by exposure to elevated temperatures in a lehr, whichsoftens the glass allowing gravity to sag or slump the glass intoconformance with the peripheral support surface. Substantially theentire support surface generally will then be in contact with theperiphery of the glass.

A related technique is press bending where a single flat glass sheet isheated to a temperature corresponding substantially to the softeningpoint of the glass. The heated sheet is then pressed or shaped to adesired curvature between male and female mold members havingcomplementary shaping surfaces. The mold member shaping surfaces mayinclude vacuum or air jets for engaging with the glass sheets. Inembodiments, the shaping surfaces may be configured to contactsubstantially the entire corresponding glass surface. Alternatively, oneor both of the opposing shaping surfaces may contact the respectiveglass surface over a discrete area or at discrete contact points. Forexample, a female mold surface may be ring-shaped surface. Inembodiments, a combination of gravity bending and press bendingtechniques can be used.

A total thickness of the glass laminate can range from about 2 mm to 5mm, with the external and/or internal chemically-strengthened glasssheets having a thickness of 1 mm or less (e.g., from 0.5 to 1 mm suchas, for example, 0.5, 0.6, 0.7, 0.8, 0.9 or 1 mm) Further, the internaland/or external non-chemically-strengthened glass sheets can have athickness of 2.5 mm or less (e.g., from 1 to 2 mm such as, for example,1, 1.5, 2 or 2.5 mm) or may have a thickness of 2.5 mm or more. Inembodiments, the total thickness of the glass sheets in the glasslaminate is less than 3.5 mm (e.g., less than 3.5, 3, 2.5 or 2.3 mm).

Exemplary glass laminate structures are illustrated in Table 2, wherethe abbreviation GG refers to a chemically-strengthened aluminosilicateglass sheet, the term “glass” refers to a non-chemically-strengthenedsoda lime (SL) glass sheet, and PVB refers to poly(vinyl butyral), whichmay optionally be an acoustic grade PVB (A-PVB).

TABLE 2 Exemplary glass laminate structures Configuration SampleInternal sheet Interlayer External sheet 1 1.5 mm SL glass 0.76-0.81 mmPVB 0.7 mm GG 2 1.5 mm SL glass 0.76-0.81 mm PVB 1.0 mm GG 3 1.5 mm SLglass 0.38-0.4 mm PVB 0.7 mm GG 4 1.5 mm SL glass 0.38-0.4 mm PVB 1.0 mmGG 5 1.6 mm SL glass 0.76 mm PVB 0.7 mm GG 6 1.6 mm SL glass 0.81 mm PVB0.7 mm GG 7 1.6 mm SL glass 1.14 mm PVB 0.7 mm GG 8 1.6 mm SL glass 1.19mm PVB 0.7 mm GG 9 1.6 mm SL glass 0.38 mm PVB 0.5 mm GG 10 1.6 mm SLglass 0.7 mm PVB 0.5 mm GG 11 2.1 mm SL glass 0.76 mm PVB 0.7 mm GG 122.1 mm SL glass 0.81 mm PVB 1.0 mm GG A 1.0 mm GG 0.76-0.81 mm PVB 1.0mm GG B 1.5 mm SL glass 0.76-0.81 mm PVB 1.5 mm SL glass

Applicants have shown that the glass laminate structures disclosedherein have excellent durability, impact resistance, toughness, andscratch resistance. As is well known among skilled artisans, thestrength and mechanical impact performance of a glass sheet or laminateis limited by defects in the glass, including both surface and internaldefects. When a glass laminate is impacted, the impact point is put intocompression, while a ring or “hoop” around the impact point, as well asthe opposite face of the impacted sheet, are put into tension.Typically, the origin of failure will be at a flaw, usually on the glasssurface, at or near the point of highest tension. This may occur on theopposite face, but can occur within the ring. If a flaw in the glass isput into tension during an impact event, the flaw will likely propagate,and the glass will typically break. Thus, a high magnitude and depth ofcompressive stress (depth of layer) is preferable.

Due to chemical strengthening, one or both of the surfaces of thechemically-strengthened glass sheets used in the disclosed hybrid glasslaminates are under compression. The incorporation of a compressivestress in a near surface region of the glass can inhibit crackpropagation and failure of the glass sheet. In order for flaws topropagate and failure to occur, the tensile stress from an impact mustexceed the surface compressive stress at the tip of the flaw. Inembodiments, the high compressive stress and high depth of layer ofchemically-strengthened glass sheets enable the use of thinner glassthan in the case of non-chemically-strengthened glass.

In the case of hybrid glass laminates, the laminate structure candeflect without breaking in response to the mechanical impact muchfurther than thicker monolithic, non-chemically-strengthened glass orthicker, non-chemically-strengthened glass laminates. This addeddeflection enables more energy transfer to the laminate interlayer,which can reduce the energy that reaches the opposite side of the glass.Consequently, the hybrid glass laminates disclosed herein can withstandhigher impact energies than monolithic, non-chemically-strengthenedglass or non-chemically-strengthened glass laminates of similarthickness.

In addition to their mechanical properties, as will be appreciated by askilled artisan, laminated structures can be used to dampen acousticwaves. The hybrid glass laminates disclosed herein can dramaticallyreduce acoustic transmission while using thinner (and lighter)structures that also possess the requisite mechanical properties formany glazing applications.

The acoustic performance of laminates and glazings is commonly impactedby the flexural vibrations of the glazing structure. Without wishing tobe bound by theory, human acoustic response peaks typically between 500Hz and 5000 Hz, corresponding to wavelengths of about 0.1-1 m in air and1-10 m in glass. For a glazing structure less than 0.01 m (<10 mm)thick, transmission occurs mainly through coupling of vibrations andacoustic waves to the flexural vibration of the glazing. Laminatedglazing structures can be designed to convert energy from the glazingflexural modes into shear strains within the polymer interlayer. Inglass laminates employing thinner glass sheets, the greater complianceof the thinner glass permits a greater vibrational amplitude, which inturn can impart greater shear strain on the interlayer. The low shearresistance of most viscoelastic polymer interlayer materials means thatthe interlayer will promote damping via the high shear strain that willbe converted into heat under the influence of molecular chain slidingand relaxation.

In addition to the glass laminate thickness, the nature of the glasssheets that comprise the laminates may also influence the soundattenuating properties. For instance, as between chemically-strengthenedand non-chemically-strengthened glass sheets, there may be small butsignificant difference at the glass-polymer interlayer interface thatcontributes to higher shear strain in the polymer layer. Also, inaddition to their obvious compositional differences, aluminosilicateglasses and soda lime glasses have different physical and mechanicalproperties, including modulus, Poisson's ratio, density, etc., which mayresult in a different acoustic response.

Examples

Conventional uniaxial strength tests, such as three- or four-pointbending tests have been used to measure the strength of glass andceramic materials. However, because the measured strength depends onedge effects as well as on the bulk material, the interpretation ofuniaxial strength test results can be challenging.

Biaxial flexure tests, on the other hand, can be used to provide astrength assessment independent of edge-induced phenomena. In a biaxialflexure test, a glass laminate is supported at three or more points nearits periphery and equidistant from its center and the laminate is thenloaded at a central position. The location of maximum tensile stressthus occurs at the center of the laminate surface and, advantageously,is independent of the edge conditions.

Exemplary planar hybrid glass laminates were subjected to a standardizedbiaxial flexure test (ECE R43 headform as detailed in Annex 7/3). Asexplained further below, when an inventive glass laminate (sample 1) wasimpacted on the non-chemically-strengthened (soda-lime) side, both glasssheets fractured. However, when the sample 1 glass laminate was impactedon the chemically-strengthened side, the non-chemically-strengthenedglass sheet fractured but the chemically-strengthened glass sheetremained intact in 50% of the samples tested.

In one test, a high loading rate impact is directed against the internal(non-chemically-strengthened) glass sheet 120. In response, both theinterior surface 124 of the internal glass sheet 120 and the exteriorsurface 112 of the external glass sheet 110 are placed in tension. Withthe magnitude of the tensile stress on the exterior surface 112 beinggreater than the tensile stress at the interior surface 124, in thisconfiguration the more moderate tensile stress on the interior surface124 is sufficient to fracture the non-chemically-strengthened glasssheet 120, while the elevated tensile stress on the exterior surface 112is sufficient to fracture the chemically-strengthened glass sheet 110 aswell. As the glass sheets fracture, the PVB interlayer deforms but keepsthe headform impact device from penetrating through the glass laminate.This is a satisfactory response under the ECE R43 headform requirement.

In a related test, the impact is directed instead against the external(chemically-strengthened) glass sheet 110. In response, the interiorsurface 114 of the external glass sheet 110 experiences a moderatetensile stress and exterior surface 122 of internal glass sheet 120experiences a higher magnitude stress. In this configuration, theelevated stress on the exterior surface 122 of the internal,non-chemically-strengthened glass sheet 120 causes thenon-chemically-strengthened glass sheet to fracture. However, themoderate tensile stress on the interior surface 114 of the externalglass sheet 110 may not be sufficient to overcome the ion-exchangedinduced compressive stress in near-surface region of thechemically-strengthened glass. In laboratory experiments, high loadingrate impact resulted in breakage of the chemically-strengthened glasssheet 110 in only two of six samples tested. In the remaining foursamples, the non-chemically-strengthened glass sheet 120 fractured butthe chemically-strengthened glass sheet 110 remained intact. All of theinventive samples exceeded the impact requirements for non-windscreenglass as set forth by the ECE R43 headform requirement.

Comparative samples A and B were also subjected to the biaxial flexuretest. Comparative sample A, which comprises a 1 mmchemically-strengthened glass sheet/0.76 mm standard PVB/1 mmchemically-strengthened glass sheet symmetric architecture, exhibited nobreakage and thus failed the ECE R43 requirement that the glass laminatemust break.

Comparison sample B comprises a 1.5 mm soda-lime glass sheet/0.76 mmstandard PVB/1.5 mm soda-lime glass sheet symmetric architecture. Bothglass sheets fractured as a result of the biaxial flexure test and thuscomparison sample B passed the ECE R43 standard (Annex 7/3). However,both glass sheets in the comparison sample B glass laminate fracturedregardless of which sheet was impacted, and thus failed to provide therobust mechanical resistance against external impact realized in thehybrid laminates. It was also noted during the testing that the recoil(i.e., bounce) of the headform was larger for comparison sample B thanfor sample 1, suggesting that the comparative architecture did notdissipate energy as effectively as the inventive example.

The head injury criterion (HIC) is a conventional metric that can beused to evaluate the safety of glass laminates. The HIC value is adimensionless quantity, which can be correlated to a probability ofsustaining an injury as a result of an impact. For internal impactevents, a lower HIC value is desirable.

For exemplary planar hybrid glass laminates, the mean HIC value forimpact on the non-chemically-strengthened side of a 1.6 mm SL/0.8 mmA-PVB/0.7 mm GG stack was 175, while the mean HIC value for impact onthe chemically-strengthened side of a 0.7 mm GG/0.8 mm A-PVB/1.6 mm SLstack was 381. For automotive glazing applications, the mean HIC valuefor impact on the chemically-strengthened (exterior) side isadvantageously greater than the mean HIC value for impact on thenon-chemically-strengthened side. For example, thechemically-strengthened side HIC value can be greater than or equal to400 (e.g., greater than or equal to 400, 450 or 500) and thenon-chemically-strengthened side HIC value can be less than or equal to400 (e.g., less than or equal to 400, 350, 300, 250, 200, 150 or 100)such that the chemically-strengthened side HIC value is at least 50(e.g., at least 50, 100, 150 or 200) greater than thenon-chemically-strengthened side value.

While this description may include many specifics, these should not beconstrued as limitations on the scope thereof, but rather asdescriptions of features that may be specific to particular embodiments.Certain features that have been heretofore described in the context ofseparate embodiments may also be implemented in combination in a singleembodiment. Conversely, various features that are described in thecontext of a single embodiment may also be implemented in multipleembodiments separately or in any suitable subcombination. Moreover,although features may be described above as acting in certaincombinations and may even be initially claimed as such, one or morefeatures from a claimed combination may in some cases be excised fromthe combination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings or figures in aparticular order, this should not be understood as requiring that suchoperations be performed in the particular order shown or in sequentialorder, or that all illustrated operations be performed, to achievedesirable results. In certain circumstances, multitasking and parallelprocessing may be advantageous

Ranges can be expressed herein as from “about” one particular value,and/or to “about” another particular value. When such a range isexpressed, examples include from the one particular value and/or to theother particular value. Similarly, when values are expressed asapproximations, by use of the antecedent “about,” it will be understoodthat the particular value forms another aspect. It will be furtherunderstood that the endpoints of each of the ranges are significant bothin relation to the other endpoint, and independently of the otherendpoint.

It is also noted that recitations herein refer to a component of thepresent disclosure being “configured” or “adapted to” function in aparticular way. In this respect, such a component is “configured” or“adapted to” embody a particular property, or function in a particularmanner, where such recitations are structural recitations as opposed torecitations of intended use. More specifically, the references herein tothe manner in which a component is “configured” or “adapted to” denotesan existing physical condition of the component and, as such, is to betaken as a definite recitation of the structural characteristics of thecomponent.

As shown by the various configurations and embodiments illustrated inthe figures, various light-weight hybrid glass laminates have beendescribed.

While preferred embodiments of the present disclosure have beendescribed, it is to be understood that the embodiments described areillustrative only and that the scope of the invention is to be definedsolely by the appended claims when accorded a full range of equivalence,many variations and modifications naturally occurring to those of skillin the art from a perusal hereof.

What is claimed is:
 1. A laminated glass article, comprising: anon-chemically strengthened external glass sheet comprising a thicknessof 3.0 mm or more, the external glass sheet providing an open convexsurface of the laminated glass article; a chemically strengthenedinternal glass sheet comprising an alkali aluminosilicate glass, athickness in a range from about 0.5 mm to about 1.5 mm, and a totalalkaline earth metal oxide content of at least 5 wt. %, the internalglass sheet providing an open concave surface of the laminated glassarticle, wherein the internal glass sheet comprises a depth of layer(DOL) of compressive stress greater than about 20 μm, wherein theinternal glass sheet and a surface compressive stress of at least 300MPa; and at least one polymer interlayer between the external andinternal glass sheets, wherein both the non-chemically strengthenedexternal glass sheet and the chemically strengthened internal glasssheet comprise distinct radii of curvature in two independentdirections.
 2. The laminated glass article of claim 1, wherein theinternal glass sheet comprises at least about 6 wt. % aluminum oxide. 3.The laminated glass article of claim 1, wherein a thickness of thepolymer interlayer is in a range from about 0.4 to about 1.2 mm.
 4. Thelaminated glass article of claim 1, wherein the external glass sheet isa soda lime glass.
 5. The laminated glass article of claim 1, whereinthe external glass sheet is annealed.
 6. The laminated glass article ofclaim 5, wherein the laminated glass article comprises an automotivewindshield.
 7. The laminated glass article of claim 1, wherein thesurface compressive stress of the internal glass sheet is greater thanor equal to 500 MPa.
 8. The laminated glass article of claim 1, whereinthe internal glass sheet comprises a central tension CT, where 40MPa<CT<100 MPa.
 9. The laminate glass article of claim 1, wherein amodulus of elasticity of the internal glass sheet is in a range fromabout 60 GPa to about 85 GPa.
 10. The laminate glass article of claim 1,wherein a modulus of elasticity of the at least one polymer interlayeris in a range from about 1 MPa to about 75 MPa.
 11. The laminated glassarticle of claim 1, wherein a surface of the external glass sheetadjacent the interlayer is acid etched.
 12. The laminated glass articleof claim 1, wherein a surface of the internal glass sheet opposite theinterlayer is acid etched.
 13. The laminated glass article of claim 1,wherein the polymer interlayer comprises a material selected from thegroup consisting of polyvinyl butyral (PVB), polycarbonate, acousticPVB, ethylene vinyl acetate (EVA), thermoplastic polyurethane (TPU), anionomer, a thermoplastic material, and combinations thereof.
 14. Thelaminated glass article of claim 1, wherein the internal glass sheetcomprises: 61-75 mol. % SiO₂; 7-15 mol. % Al₂O₃; 0-12 mol. % B₂O₃; 9-21mol. % Na₂O; 0-4 mol. % K₂O; 0-7 mol. % MgO; and 0-3 mol. % CaO.
 15. Thelaminated glass article of claim 1, wherein the internal glass sheetcomprises Al₂O₃, B₂O₃, and at least 60 mol. % SiO₂, and the ratio(Al₂O₃+B₂O₃)/(the total alkaline earth metal oxide content)>1, whereAl₂O₃ and B₂O₃ are expressed in mol. %.
 16. The laminated glass articleof claim 1, wherein the thickness of the chemically strengthenedinternal glass sheet is less than 1.0 mm.
 17. The laminated glassarticle of claim 16, wherein the thickness of the chemicallystrengthened internal glass sheet greater than or equal to 0.5 mm andless than or equal to 0.7 mm.
 18. The laminated glass article of claim1, wherein the chemically strengthened internal glass is made by fusiondrawing.
 19. The laminated glass article of claim 1, wherein thelaminated glass article withstands an impact energy higher than amonolithic glass article formed of non-chemically strengthened glasshaving the same overall thickness.